Percutaneous access for systems and methods of treating sleep-related disordered breathing

ABSTRACT

Systems and methods are described and illustrated for percutaneously implanting a stimulation lead for treating sleep-related disordered breathing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.15/345,096, filed Nov. 7, 2016, which is a Continuation of U.S. patentapplication Ser. No. 13/262,434, filed Dec. 22, 2011, now U.S. Pat. No.9,486,628, which is a 371 international application of PCT/US10/29253,filed Mar. 30, 2010, which claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/165,110, filed Mar. 31, 2009, all of which areincorporated herein by reference.

BACKGROUND

The present disclosure relates generally to an implantable stimulationsystem for stimulating and monitoring soft tissue in a patient, and moreparticularly, the present disclosure relates to systems and methods ofusing percutaneous delivery of a stimulation lead to treat sleep-relateddisordered breathing, such as obstructive sleep apnea and otherdisorders, and relates to various configurations of a stimulationelectrode portion of a stimulation lead.

Sleep apnea generally refers to the cessation of breathing during sleep.One type of sleep apnea, referred to as obstructive sleep apnea (OSA),is characterized by repetitive pauses in breathing during sleep due tothe obstruction and/or collapse of the upper airway, and is usuallyaccompanied by a reduction in blood oxygenation saturation.

One treatment for obstructive sleep apnea has included the delivery ofelectrical stimulation to the hypoglossal nerve, located in the neckregion under the chin. Such stimulation therapy activates the upperairway muscles to maintain upper airway patency. In treatment of sleepapnea, increased respiratory effort resulting from the difficulty inbreathing through an obstructed airway is avoided by synchronizedstimulation of an upper airway muscle or muscle group that holds theairway open during the inspiratory phase of breathing. For example, thegenioglossus muscle is stimulated during treatment of sleep apnea by acuff electrode placed around the hypoglossal nerve.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects and features of the present disclosure will be appreciated asthe same becomes better understood by reference to the followingdetailed description of the embodiments of the present disclosure whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic illustration of an implantable stimulation system,according to an embodiment of the present disclosure;

FIG. 2 is a schematic illustration of a block diagram of an implantablestimulation system, according to an embodiment of the presentdisclosure;

FIG. 3 is a schematic illustration of a block diagram of a sensingmonitor, according to an embodiment of the present disclosure;

FIG. 4 is a schematic illustration of a percutaneous access systemincluding a site locator tool, a stimulation monitor, and a responseevaluation array, according to an embodiment of the present disclosure;

FIG. 5 is a schematic illustration of a method of identifying astimulation site, according to an embodiment of the present disclosure;

FIG. 6A is a side plan view schematically illustrating a stimulationlead introduction tool, according to an embodiment of the presentdisclosure;

FIG. 6B is a sectional view as taken along lines 6B-6B of FIG. 6A,according to an embodiment of the present disclosure;

FIG. 6C is a side plan view schematically illustrating a stimulationlead introduction tool, according to an embodiment of the presentdisclosure;

FIG. 7A is sectional view schematically illustrating insertion of a testlocator tool, according to an embodiment of the present disclosure;

FIG. 7B is sectional view schematically illustrating a configurationupon insertion of an introduction tool, according to an embodiment ofthe present disclosure;

FIG. 7C is sectional view schematically illustrating a configurationupon removal of a locator tool, according to an embodiment of thepresent disclosure;

FIG. 7D is sectional view schematically illustrating a configurationupon insertion of a stimulation lead via the introduction tool,according to an embodiment of the present disclosure;

FIG. 7E is sectional view schematically illustrating a configuration ofthe stimulation lead upon removal of the introduction tool, according toan embodiment of the present disclosure;

FIG. 8A is a side plan view schematically illustrating a stimulationlead including a distal electrode portion, according to an embodiment ofthe present disclosure;

FIG. 8B is a bottom plan view of the stimulation lead of FIG. 8Aincluding a schematic illustration of a stimulation electrode portion,according to an embodiment of the present disclosure;

FIG. 8C is a perspective view of the stimulation lead of FIGS. 8A-8Bincluding a schematic illustration of an anchoring mechanism, accordingto an embodiment of the present disclosure;

FIG. 8D is a perspective view of a distal portion of a stimulation leadintroduction tool, according to an embodiment of the present disclosure;

FIG. 8E is a sectional view of a distal portion of a stimulation leadintroduction tool and a stimulation lead extending therethrough,according to an embodiment of the present disclosure;

FIG. 8F is partial end view of a distal portion of a stimulation leadhaving convex-shaped electrode portion, according to an embodiment ofthe present disclosure;

FIG. 8G is partial end view of a distal electrode portion of astimulation lead having a concave-shaped electrode portion, according toan embodiment of the present disclosure;

FIG. 9 is a perspective view of a stimulation lead including ananchoring system, according to an embodiment of the present disclosure;

FIG. 10 is a perspective view of an alternate anchoring system,according to an embodiment of the present disclosure;

FIG. 11 is a sectional view schematically illustrating a method ofpercutaneous delivery of a stimulation lead, according to an embodimentof the present disclosure;

FIG. 12 is a side plan view of an introduction tool employed in themethod associated with FIG. 11, according to an embodiment of thepresent disclosure;

FIG. 13 is a bottom plan view of a distal electrode portion of astimulation lead, according to an embodiment of the present disclosure;

FIG. 14A is an enlarged sectional view schematically illustrating aselectively deployable anchoring mechanism of the introduction tool ofFIGS. 11-12, according to an embodiment of the present disclosure;

FIG. 14B is an enlarged side view schematically illustrating theanchoring mechanism in a deployed state relative to the surroundingtissue, according to an embodiment of the present disclosure;

FIG. 14C is a sectional view schematically illustrating a distalelectrode portion of a stimulation lead secured relative to a nerve viaan anchoring mechanism, according to an embodiment of the presentdisclosure;

FIG. 15 is a perspective view schematically illustrating abio-absorbable stimulation system prior to absorption, according to anembodiment of the present disclosure;

FIG. 16 is a perspective view schematically illustrating thebio-absorbable stimulation system of FIG. 15 after absorption, accordingto an embodiment of the present disclosure;

FIG. 17A is an enlarged side plan view of an electrode portion of thestimulation system of FIGS. 15-16, according to an embodiment of thepresent disclosure;

FIG. 17B is a sectional view as taken along lines 17B-17B of FIG. 16,according to an embodiment of the present disclosure;

FIG. 18 is a side plan view of a bio-absorbable, stent-electrodestimulation lead, according to an embodiment of the present disclosure;

FIG. 19 is a side plan view schematically illustrating deployment of thestent-electrode stimulation lead of FIG. 18 relative to a nerve,according to an embodiment of the present disclosure;

FIG. 20 is a sectional view schematically illustrating anchoring of anelectrode against a nerve after absorption of the bio-absorbable stentportion of the stimulation lead, according to an embodiment of thepresent disclosure;

FIG. 21 is a side plan view schematically illustrating the electrodes ofthe stimulation lead against the target nerve after absorption of thebio-absorbable stent portion of the stimulation lead, according to anembodiment of the present disclosure.

FIG. 22 is a perspective view schematically illustrating abio-absorbable electrode portion of a stimulation lead, according to anembodiment of the present disclosure;

FIG. 23 is a perspective view schematically illustrating implantedelectrodes of the stimulation lead of FIG. 22 prior to absorption,according to an embodiment of the present disclosure;

FIG. 24 is a perspective view schematically illustrating the implantedelectrodes of the stimulation lead of FIG. 22 after absorption,according to an embodiment of the present disclosure;

FIG. 25 is a top plan view of an electrode portion of a stimulationlead, according to an embodiment of the present disclosure;

FIG. 26 is a top plan view schematically illustrating a stimulationsystem as deployed relative to a nerve, including the electrode portionof a stimulation lead and an insulator shield, according to anembodiment of the present disclosure;

FIG. 27 is a sectional view as taken along lines 27-27 of FIG. 26,according to an embodiment of the present disclosure;

FIG. 28 is a top plan view of an electrode portion of a stimulationlead, according to an embodiment of the present disclosure;

FIG. 29 is a side view schematically illustrating an insulator shieldreleasably connected, via a coupling mechanism, to an electrode portionof a stimulation lead, according to an embodiment of the presentdisclosure;

FIG. 30 is a sectional view schematically illustrating one aspect of amethod of percutaneous access for a stimulation system, according to anembodiment of the present disclosure;

FIG. 31 is a top elevational view schematically illustrating one aspectof the method of percutaneous access, according to an embodiment of thepresent disclosure; and

FIG. 32 is a sectional view schematically illustrating another aspect ofthe method of percutaneous access, according to an embodiment of thepresent disclosure.

DESCRIPTION OF EMBODIMENTS

The following detailed description is merely exemplary in nature and isnot intended to limit the present disclosure or the application and usesof the present disclosure. Furthermore, there is no intention to bebound by any expressed or implied theory presented in the precedingtechnical field, background, or the following detailed description.

Embodiments of the present disclosure provide implantable medicaldevices, systems, and methods for treating sleep-related disorderedbreathing, such as but not limited to obstructive sleep apnea. In thesemethods and systems, stimulation is provided to the hypoglossal nerve(or another target nerve) through a lead system that is deliveredpercutaneously or delivered using other minimally invasive techniques.In addition, embodiments of the present disclosure include variousconfigurations of the stimulation electrode portion of a stimulationlead.

FIG. 1 is a schematic diagram of an implantable stimulation system thatincludes a percutaneously placed stimulation electrode, according to anembodiment of the present disclosure. As illustrated in FIG. 1, anexample of an implantable stimulation system 10 according to oneembodiment of the present disclosure includes an implantable pulsegenerator (IPG) 55, capable of being surgically positioned within apectoral region of a patient 20, and a stimulation lead 52 electricallycoupled with the IPG 55 via a connector (not shown) positioned within aconnection port of the IPG 55. The lead 52 includes a stimulationelectrode portion 65 and extends from the IPG 55 so that the stimulationelectrode portion 65 is positioned in contact with a desired nerve, suchas the hypoglossal nerve 53 of the patient 10, to enable stimulation ofthe nerve 53, as described below in detail. An exemplary implantablestimulation system in which lead 52 may be utilized, for example, isdescribed in U.S. Pat. No. 6,572,543 to Christopherson et al., and whichis incorporated herein by reference in its entirety. In one embodiment,the lead 52 further includes at least one sensor portion 60(electrically coupled to the IPG 55 and extending from the IPG 55)positioned in the patient 10 for sensing respiratory effort, such asrespiratory pressure.

In some embodiments, the sensor portion 60 detects respiratory patterns(e.g., inspiration, expiration, respiratory pause, etc.) in order totrigger activation of an electrode portion to stimulate a target nerve.Accordingly, with this arrangement, the IPG 55 (FIG. 1) receives sensorwaveforms from the respiratory sensor portion 60, thereby enabling theIPG 55 to deliver electrical stimulation synchronously with inspiration(or another aspect of the respiratory pattern related to inspiration)according to a therapeutic treatment regimen in accordance withembodiments of the present disclosure. It is also understood that therespiratory sensor portion 60 is powered by the IPG 55 and the IPG 55also contains internal circuitry to accept and process the impedancesignal from the stimulation lead 52.

In some embodiments, the sensor portion 60 is a pressure sensor. In oneaspect, the pressure sensor in this embodiment detects pressure in thethorax of the patient. In another aspect, the sensed pressure could be acombination of thoracic pressure and cardiac pressure (e.g., bloodflow). With this configuration, the controller is configured to analyzethis pressure sensing information to detect the respiratory patterns ofthe patient.

In some other embodiments, the respiratory sensor portion 60 comprises abio-impedance sensor or pair of bio-impedance sensors and can be locatedin regions other than the pectoral region. In one aspect, such animpedance sensor is configured to sense a bio-impedance signal orpattern whereby the control unit evaluates respiratory patterns withinthe bio-impedance signal. For bio-impedance sensing, in one embodiment,electric current will be injected through an electrode portion withinthe body and an electrically conductive portion of a case of the IPG 55(FIG. 3A) with the voltage being sensed between two spaced apartstimulation electrode portions (or also between one of the stimulationelectrode portions and the electrically conductive portion of the caseof IPG 55) to compute the impedance.

In some embodiments, system 10 also comprises additional sensors tofurther obtain physiologic data associated with respiratory functions.For example, system 10 may include various sensors (e.g., sensors 67,68, 69 in FIG. 1) distributed about the chest area for measuring atrans-thoracic bio-impedance signal, an electrocardiogram (ECG) signal,or other respiratory-associated signals.

In some embodiments, the sensing and stimulation system for treatingobstructive sleep apnea is a totally implantable system which providestherapeutic solutions for patients diagnosed with obstructive sleepapnea. In other embodiments, one or more components of the system arenot implanted in a body of the patient. A few non-limiting examples ofsuch non-implanted components include external sensors (respiration,impedance, etc.), an external processing unit, or an external powersource. Of course, it is further understood that the implantedportion(s) of the system provides a communication pathway to enabletransmission of data and/or controls signals both to and from theimplanted portions of the system relative to the external portions ofthe system. The communication pathway includes a radiofrequency (RF)telemetry link or other wireless communication protocols.

Whether partially implantable or totally implantable, the system isdesigned to stimulate the hypoglossal nerve during inspiration tothereby prevent obstructions or occlusions in the upper airway duringsleep. In one embodiment, the implantable system comprises animplantable pulse generator (IPG), a peripheral nerve cuff stimulationlead, and a pressure sensing lead.

FIG. 2 is a block diagram schematically illustrating an implantablestimulation system 100, according to one embodiment of the presentdisclosure. In one embodiment, system 100 comprises at leastsubstantially the same features and attributes as system 10 of FIG. 1.As illustrated in FIG. 2, system 100 includes a sensing module 102, astimulation module 104, a therapy module 106, and a patient managementmodule 108. In one embodiment, the IPG 109 of therapy module 106comprises at least substantially the same features and attributes as IPG55 of Figure

Via an array of parameters, the sensing module 102 receives and trackssignals from various physiologic sensors (such as a pressure sensor,blood oxygenation sensor, acoustic sensor, electrocardiogram (ECG)sensor, or impedance sensor) in order to determine a respiratory stateof a patient, whether or not the patient is asleep or awake, and otherrespiratory-associated indicators, etc. Such respiratory detection maybe received from either a single sensor or any multiple of sensors, orcombination of various physiologic sensors which may provide a morereliable and accurate signal.

For example, in one embodiment, the sensing module 102 comprises asensing monitor 120, as illustrated in FIG. 3. The sensing monitor 120includes a body parameter 130, which includes at least one of aposition-sensing component 132 or a motion-sensing component 134. In oneembodiment, the motion-sensing component 134 tracks sensing of “seismic”activity (via an accelerometer or a piezoelectric transducer) that isindicative of walking, body motion, talking, etc. In another embodiment,the position-sensing component 132 tracks sensing of a body position orposture via an accelerometer or other transducer. In some embodiments,body parameter 130 utilizes signals from both the position-sensingcomponent 132 and the motion-sensing component 134.

In some embodiments, sensing monitor 120 additionally comprises one ormore of the following parameters: an ECG parameter 136; a time parameter138; a bio-impedance parameter 140; a pressure parameter 142; and ablood oxygen parameter 144. In one aspect, the pressure parameter 142includes a respiratory pressure component 143. In one aspect, the timeparameter 142 tracks time generally (e.g. time intervals, elapsed time,etc.) while in other aspects, the time parameter 142 tracks the time ofday in addition to or instead of the general time parameters. In anotheraspect, the time parameter 142 can be used to activate or deactivate atherapy regimen according to a time of day.

It is also understood that system 100 (FIG. 2) would include, or beconnected to, the analogous physiologic sensor (e.g., LED-type oroptical tissue perfusion oxygen saturation) implanted within or attachedto the body of the patient to provide data to each one of theirrespective parameters (e.g., blood oxygenation parameter 144) of thesensing monitor 120. In some embodiments, sensing monitor 120 alsoincludes a target nerve parameter 146 which represents physiologic dataregarding the activity of a nerve to be stimulated, such as thehypoglossal nerve, including specification of the trunk and/or one ormore branches of the hypoglossal nerve. In yet other embodiments,sensing monitor 120 also includes an acoustic sensing parameter 147which represents physiologic data from respiratory airflow or cardiacactivity that is sensed acoustically and that is indicative ofrespiratory effort.

In further reference to FIG. 2, therapy manager 106 of system 100 isconfigured to automatically control initiation, termination, and/oradjustment of a sleep apnea therapy, in accordance with the principlesof the present disclosure. Therapy manager 106 also tracks and appliesvarious treatment parameters, such as an amplitude, pulse width,electrode polarity, duration, and/or frequency of a neuro-stimulationsignal, in accordance with a treatment protocol programmed into thetherapy manager 106.

In one embodiment, therapy manager 106 comprises one or more processingunits and associated memories configured to generate control signalsdirecting the operation of system 100, including at least sensing module102, therapy manager 106, stimulation module 104, and patient managementmodule 108. In particular, in response to or based upon commandsreceived via an input and/or instructions contained in the memoryassociated with the controller in response to physiologic data gatheredvia the sensing module 102, therapy manager 106 generates controlsignals directing operation of stimulation module 104 to selectivelycontrol stimulation of a target nerve, such as the hypoglossal nerve, torestore airway patency and thereby reduce or eliminate apnea events.

With this in mind, therapy manager 106 acts to synthesize respiratoryinformation, to determine suitable stimulation parameters based on thatrespiratory information, and to direct electrical stimulation to thetarget nerve. While any number of physiologic parameters can be usedwith varying success to detect an apnea, in one embodiment of thepresent disclosure, the sensing module 102 detects apneas via a thoracicbio-impedance parameter. In particular, a measurement of thoracicimpedance is used to track the relative amplitude of the respiratorywaveform. Physiologically speaking, the bio-impedance of the lungsvaries as the lungs fill and empty with air. Accordingly, thoracicimpedance increases during inspiration and decreases during expiration.In another aspect, a varying respiratory drive will also cause theamplitude of the bio-impedance to vary, with a larger respiratory driveincreasing the signal amplitude of the bio-impedance.

Upon obtaining the bio-impedance signal, the bio-impedance signal isfurther processed to identify an average peak amplitude over time. Anapnea is detected by further identifying cyclic amplitude variationsthat occur for a duration substantially similar to the already knownduration of a typical apnea event.

For purposes of this application, the term “processing unit” shall meana presently developed or future developed processing unit that executessequences of instructions contained in a memory. Execution of thesequences of instructions causes the processing unit to perform stepssuch as generating control signals. The instructions may be loaded in arandom access memory (RAM) for execution by the processing unit from aread only memory (ROM), a mass storage device, or some other persistentstorage, as represented by a memory associated with the controller. Inother embodiments, hard wired circuitry may be used in place of or incombination with software instructions to implement the functionsdescribed. For example, the controller may be embodied as part of one ormore application-specific integrated circuits (ASICs). Unless otherwisespecifically noted, the controller is not limited to any specificcombination of hardware circuitry and software, nor limited to anyparticular source for the instructions executed by the processing unit.

In general terms, the stimulation module 104 of system 100 is configuredto generate and apply a neuro-stimulation signal via electrode(s) (suchas stimulation electrode(s) 65) according to a treatment regimenprogrammed by a physician and/or in cooperation with therapy manager106.

In general terms, the patient management module 108 is configured tofacilitate communication to and from the IPG 109 in a manner familiar tothose skilled in the art. Accordingly, the patient management module 108is configured to report activities of the IPG 109 (including sensedphysiologic data, stimulation history, number of apneas detected, etc.)and is configured to receive initial or further programming of the IPG109 from an external source, such as a patient programmer, clinicianprogrammer, etc.

In accordance with at least one embodiment of the present disclosure, astimulation site locator tool 200 of a percutaneous delivery system 201is schematically illustrated in the plan view of FIG. 4. In generalterms, the site locator tool 200 is configured to facilitate identifyinga target or optimal stimulation site and/or a point of penetration toperform a percutaneous delivery of a stimulation lead near the targetstimulation site. As shown in FIG. 4, site locator tool 200 includes aneedle 210 extending from a handle 212. The needle 210 includes a distaltip 214, needle body 216, and a series of depth markers 218 extendingalong the needle body 216. The needle 210 extends proximally from thedistal tip 214 and through handle 212, terminating at proximal end 219.At proximal end 219, a connection port 236 provides releasableelectrical connection between the needle 210 and a stimulation monitor(as later described in more detail), which provides an electricalstimulation signal at distal tip 214.

Referring again to FIG. 4, in one aspect, the needle body 216 includes adielectric coating on its outer surface while a conductive surface ofthe distal tip 214 is exposed to allow electrical conductivity betweenthe distal tip 214 and the tissue within the body. The depth markers 218are visible to the eye and may in some embodiments, be formed of amaterial that is readily visible through radiographic and/or ultrasoundvisualization techniques, as later described in more detail.

Moreover, it is understood that various surgical visualizationtechniques can be used in association with the embodiments of thepresent disclosure to assist in determining the location of the sitelocator tool 200, the stimulation electrode portion, and othercomponents involved in percutaneous delivery of the stimulation lead.

By inserting the site locator tool 200 percutaneously at variouslocations near or adjacent to the hypoglossal nerve (in cooperation witha stimulation monitor) the path of the hypoglossal nerve is identifiedbased on the type and magnitude of neurogenic responses, such asneuromuscular responses, observed upon application of the teststimulation signal at those various test locations. In this way, thosetest locations that exhibit a neuromuscular response indicative of aquality nerve capture are used to identify the optimal or target site toplace a stimulation electrode portion of a stimulation lead. Theseobserved responses are also used to identify a skin insertion point atwhich the percutaneous access will be initiated.

In some embodiments, the neuro-stimulation signal is applied at a singlestimulation site along the hypoglossal nerve as illustrated in FIG. 1(see stimulation electrode portion 65). However, in other embodiments,the neuro-stimulation signal of a sleep apnea therapy is applied fromtwo or more of multiple locations spaced longitudinally along thehypoglossal nerve. In such an arrangement, the separate, spaced apartstimulation electrode portions can be activated simultaneously oractivated at different times. With this in mind, it is understood thatthe percutaneous access method can be applied to locate more than onesite along the hypoglossal nerve to identify placement of severaldifferent stimulation electrode portions.

In further reference to FIG. 4, in cooperation with the site locatortool 200 a stimulation monitor, such as a nerve integrity monitor 250 (astand alone monitor or a monitor integrated into a sleep apnea physicianprogrammer 108, such as programmer 108 in FIG. 2), is connected to thesite locator tool 200 via connector 237. The stimulation monitor is usedto aide the physician in determining proper electrode placement viastimulation applied via the site locator tool 200. In one embodiment, anIPG 55 (FIG. 1) or IPG 109 (FIG. 2) can be used as the stimulationmonitor. In some embodiments, the stand-alone nerve integrity monitor250 comprises at least substantially the same features and attributes asthe nerve integrity monitor described in U.S. Pat. No. 6,334,068,entitled INTRAOPERATIVE NEUROELECTROPHYSIOLOGICAL MONITOR, issued onDec. 25, 2001, and which is hereby incorporated by reference in itsentirety. In other embodiments, other nerve integrity monitors or anequivalent array of instruments (e.g., a stimulation probe andelectromyography system) are used to apply the stimulation signal andevaluate the response of the muscle innervated by the target nerve.

As shown in FIG. 4, in some embodiments nerve integrity monitor 250comprises stimulation module 252 and a response module 254 that includeselectromyography monitoring electronics (EMG) 256. In addition, FIG. 4further illustrates a response evaluation array 275, according to oneembodiment of the present disclosure. The response evaluation array 275provides one or more mechanisms to evaluate the effectiveness of atarget site for stimulating a target nerve and to identify an entrypoint for percutaneous delivery of the stimulation electrode portion. Inone embodiment, upon stimulation applied at a potential target site, theresponse array 275 includes: (1) observing or measuring the extent andlocation (an extension of the base of the tongue is preferred overextension of the tip) of tongue protrusion 278 (indicated by arrow P);(2) observing or measuring the extent of increased cross-sectional area(indicated by arrow W) of an upper respiratory airway 277, with theobservation/measurement being performed via endoscopy, ultrasound, orother visualization techniques; and/or (3) measuring the extent of anEMG response 280 (measured via EMG electronics 256 of monitor 250) ofone or more muscles.

Accordingly, with this in mind, monitor 250 and one or more aspects ofthe response array 275 are used to evaluate the positioning of sitelocator tool 200 relative to a potential stimulation site on a targetnerve. In one aspect, a repetitive stimulation pattern is applied fromthe stimulation module 252 of nerve integrity monitor 250 to the distaltip 214 of site locator tool 200, as the site locator tool 200 ispercutaneously inserted into various locations adjacent to the targetnerve and into the target nerve. In some embodiments, the appliedstimulation pattern is a 1 second burst of stimulation every 3 seconds,a ramping stimulation pattern, and/or a physician controlled burst. Inanother aspect, electromyography (EMG) monitoring electronics 256 of thenerve integrity monitor 250 enables measuring a muscle response to thenerve stimulation applied during the iterative percutaneous insertion ofthe site locator tool 200. Accordingly, as further shown in FIG. 4, finewire electrodes 282 (or similar) are connected in electricalcommunication with EMG electronics 256 of the nerve integrity monitor250 and are used to continuously monitor the muscle activity in responseto the stimulation patterns applied via site locator tool 200. Usingthis arrangement, this closed loop feedback will allow the physician toobtain real-time feedback of a position of the site locator tool 200(relative to the hypoglossal nerve) and feedback regarding the expectedability of a percutaneously implanted electrode lead to capture thetarget nerve.

In one embodiment of the present disclosure, as illustrated in FIG. 5, amethod 300 of treating apnea includes identifying an optimal site tolocate stimulation electrode portion 65 (FIG. 1) along a length of thehypoglossal nerve that will result in a desired stimulation of thehypoglossal nerve and treatment of sleep apnea. In particular, asillustrated at 302 in FIG. 5, the site locator tool 200 is insertedpercutaneously (through the skin toward the target nerve) into varioustest stimulation sites at or around the hypoglossal nerve. For example,as further shown in the diagram 400 of FIG. 7A, needle 210 extendsthrough percutaneous access path 408 such that distal tip 214 becomeselectrically coupled relative to nerve 410 at one of several potentialstimulation sites (e.g., A, B, C) with proximal handle 212 external toskin surface 402. Via surgical navigation techniques, the graduationmarkers 218 enable measuring a depth of insertion through skin 402 andother subcutaneous tissues 404, 405 surrounding nerve 410. While FIGS. 4and 7A illustrate just a few such markers 218 for illustrative purposes,it will be understood that markers 218 would extend along a length orsubstantial length of needle 210 and that the spacing of such markers218 may vary from that shown in FIGS. 4 and 7A. It will be understoodthat various components of tool 200 and the surrounding tissues areenlarged and/or minimized for illustrative purposes.

At each test site, a pre-determined profile of electrical stimuli isapplied to identify one or more optimal or preferred target sites on thehypoglossal nerve. As illustrated at 304 in FIG. 5, the optimal orpreferred target site are identified from among the test sites basedobserving or measuring at least: (1) a degree of tongue protrusion; (2)the size of cross-sectional area of the upper airway; (3) a best EMGresponse indicative of maintaining airway patency; (4) a lack ofresponse from non-target muscles; and/or (5) a twitch from the tonguemuscle and/or laryngeal muscle. In one aspect, an optimal or preferredtarget stimulation site is correlated with the greatest impact onmaintaining airway patency during inspiration. After identifying atarget site, method 300 includes identifying a percutaneous accesspathway to the target site. In one aspect, this identification includesidentifying a skin entry site (such as D, E, F, or G), which may or maynot be directly above the target stimulation site on the hypoglossalnerve. Finally, it is understood that these steps 302-306 can berepeated iteratively, as necessary, until all the optimal stimulationlocations along the target nerve are identified.

In one aspect, in evaluating various test stimulation sites, it will beunderstood that the magnitude of the measured response will beindicative how close the site locator tool 200 is to the hypoglossalnerve and/or which part of the hypoglossal nerve is being stimulated.For example, the distance between the site locator tool 200 and thehypoglossal nerve and the strength of the measured response is expressedin decreasing exponential relationship. In other words, as the distanceaway from the hypoglossal nerve increases, there is an exponentialdecrease in the magnitude of the measured response. In one aspect, thedistance refers to a distance measured in three dimensions relative tothe path of the hypoglossal nerve, as any given test site will involve:a lateral distance extending generally perpendicular relative to alongitudinal axis of the target nerve; (2) a vertical distance relativeto the target nerve; and (3) a longitudinal distance extending generallyparallel relative to a longitudinal axis of the target nerve. With thisin mind, it is understood that as multiple potential sites are tested, apattern is identified that highlights the best or optimal stimulationsite(s) from among the test sites. In addition, other surgicalnavigation techniques can be used in cooperation with the application ofthe test stimulus to further pinpoint the optimal/preferred stimulationsites via visualizing the site locator tool 200 within the targetanatomical environment at the time that the responses are measured.

In some embodiments, in evaluating multiple potential stimulation sitesalong the hypoglossal nerve, at each potential stimulation site themethod 300 applies the pre-determined electrical stimuli as astimulation signal with differing values for each signal parameter(e.g., pulse width, electrode polarity, frequency, duration, andamplitude) to determine which combination of values yields the bestimpact of the stimulation signal upon the target nerve at a potentialsite. In this way, each potential site is evaluated under conditions inwhich the stimulation signal would actually be applied were thatpotential site chosen as an optimal site for stimulation. In oneembodiment, this determination of an optimal stimulation site viaevaluating each of the stimulation parameters employs therapy module 106(including IPG 109) in cooperation with stimulation module 104, a sitelocator tool 200, and patient programming module 108, as previouslydescribed in association with FIGS. 1-4.

In one aspect, an optimal stimulation site identified via the sitelocator tool 200 is preserved to allow an accurate delivery of thestimulation electrode portion of the stimulation lead to that site.Accordingly, in some embodiments, while maintaining needle 210 in itsinserted position in the optimal site along the hypoglossal nerve,handle 212 is removed from needle body 216 while maintaining the distaltip 214 in a coupled relationship to nerve 410, and then a leadintroduction tool is slidably advanced over the proximal portion 219 ofneedle 210 of site locator tool 200 to produce the configuration shownin FIG. 7B, as will be further described later.

In general terms, a stimulation lead is inserted percutaneously toresult in a distal portion of the stimulation lead being closelyadjacent to a target stimulation site of a nerve. In some embodiments,an introducing mechanism is used to initiate and develop a percutaneousaccess pathway to the target stimulation site and facilitatesintroduction of the stimulation lead therethrough. While variousdifferent shapes and forms of lead introduction tools can be used, FIG.6A illustrates one exemplary embodiment of a lead introduction tool 350.As shown in FIG. 6A, lead introduction tool 350 includes a cannula 360extending through and supported by handle 362. Cannula 360 includes acurved distal portion 375 with a body portion 366 extending proximallyfrom distal portion 375 to a proximal portion 369 within handle 362. Inone aspect, cannula 360 includes a series of graduation depth markers368 to permit measurement of the desired depth of insertion. While FIGS.6A and 7B illustrate just a few such markers 368 for illustrativepurposes, it will be understood that markers 368 would extend along alength or substantial length of cannula 360 and that the spacing of suchmarkers 368 may vary from that shown in FIGS. 6A and 7B. In someembodiments, at least some of the depth markers 368 are also formed of aradiopaque material to enable visualization under fluoroscopy or othervisualization techniques to ensure a proper orientation, position, andplacement of the cannula 360 relative to a target nerve and/or othertissues, structures, etc. It also will be understood that at least someconductive portions of cannula 360, needle 210 will be visualized underfluoroscopy or other visualization techniques to further aid ensuringproper placement, orientation, and/or position of those respectiveelements.

As shown in the sectional view of FIG. 6B, cannula 360 defines a lumen370 that extends throughout body portion 366. In general terms, cannula360 is a generally tubular structure with electrically conductiveproperties. Accordingly, as shown in FIG. 6B, in one aspect, bodyportion 366 has a dielectric or insulative coating 367 on its outersurface while distal tip 364 of cannula 360 omits a dielectric coating.

In one embodiment, distal tip 364 includes an end opening 390 sized andshaped to facilitate passage of a stimulation lead therethrough.Moreover, curved distal portion 372 is formed of a generally resilient,flexible material. Accordingly, upon slidably advancing cannula body 366over a pre-placed site locator tool 200, as illustrated in FIGS. 4 and7A, curved distal portion 372 assumes a generally straight shape to aidits insertion percutaneously through skin 402 and tissues 404, 405 at anangle generally perpendicular to the hypoglossal nerve, as shown in FIG.7B. In addition, in this position, the proximal portion and/or handle362 of tool 350 remains external to skin surface 402. It will beunderstood that in some embodiments, in the absence of site locator tool200, a stiffener or stylet, as known to those skilled in the art, can beused to maintain the cannula body 366 in a straight configuration duringits insertion percutaneously. One generally example of such stylets isdescribed and illustrated in Buckberg U.S. Pat. No. 5,226,427, which ishereby incorporated by reference in its entirety.

In its straightened shape, cannula 310 has a shape substantially similarto that shown for tool 380 that is later described in association withFIG. 6C. Referring again to FIG. 6A, once the distal tip 364 is locatedat a desired depth, the locator tool 200 (or other stiffener) is removedcausing the curved distal portion 372 to relax and resume its generallycurved shape, as shown in FIG. 7C. This relaxation, in turn, orientsdistal end opening 378 to be generally parallel to the hypoglossal nerve410 as shown in FIG. 7C, thereby assuming a position suitable to directa stimulation lead to be slidably advanced along the hypoglossal nerveto a desired stimulation site. In some embodiments, upon suchrelaxation, the distal end opening 378 is oriented at a generally obtuseangle relative to the generally straight proximal portion of the cannula310.

In some embodiments, as will be understood by those skilled in the art,when identifying the optimal stimulation site (A) from among multiplepotential sites (e.g. A, B, C, etc.), the site locator tool 200 wouldalso be used to identify a corresponding entry point (e.g., D, E, F, G,etc.) of the lead introduction tool that is distal or proximal to theoptimal stimulation site (e.g., A), as illustrated in FIGS. 7A-7E. Inone embodiment, the spacing (along an axis generally parallel to thehypoglossal nerve) between the entry point at the skin surface (e.g., E)and the optimal stimulation site (A) on the hypoglossal nerve issubstantially equal to the distance (D1) that distal end opening 378extends from the generally perpendicular (relative to the hypoglossalnerve) orientation of cannula body portion 366 when inserted.

In another embodiment, the spacing between the skin entry point and theoptimal stimulation site is configured to further account for the length(represented by D2 in FIG. 6A) of the stimulation lead (including theelectrode portion as represented by dashed lines 395) that would extendout of end opening 378 to deliver the electrode portion of thestimulation lead at the target stimulation site. This arrangementfurther insures that the final placement of the electrode portion of thestimulation lead accurately corresponds to the previously identifiedoptimal or target stimulation site (e.g. A in FIGS. 7A-7E). However, itwill be further understood that in some embodiments, the distal end ofthe stimulation lead is positioned to extend beyond the targetstimulation site marked at distance D2 to ensure that the targetstimulation site remains generally centered along the length of theelectrode portion (e.g., electrode array 442 of portion 440 as laterdescribed in relation to FIG. 8A-8C) of the stimulation lead. In suchembodiments, the distance D2 corresponds to a length no more than alength of the electrode portion and likely less than (e.g. aboutone-quarter, one-half, or three-quarters) a length of the electrodeportion (e.g. electrode array 442 of portion 440 in FIGS. 8A-8C).

Accordingly, in this embodiment the total spacing (along an axisgenerally parallel to a longitudinal axis of the hypoglossal nerve inthis region) between the skin entry point and the optimal stimulationsite would be the combination of the distances D1 and D2. With this inmind, in one embodiment, after the optimal stimulation site (e.g. A fromamong A, B, C, etc.) is identified via the site locator tool 200, thesite locator tool 200 is used to trace the path of the hypoglossal nerve(or other suitable anatomical landmark) to identify a skin entry point(e.g. E in FIG. 7A-7B) for the lead introduction tool 350 that spacedapart from the optimal stimulation site (e.g. A in FIGS. 7A-7B) by adistance of D1 plus D2.

In one aspect, tracking these distances D1 and D2 greatly enhances theintroduction of the stimulation lead to arrive at the optimalstimulation site because of the relative absence of significantanatomical structures (e.g., bone canals, protuberances, etc.) in theregion of the hypoglossal nerve that is to be stimulated.

In another embodiment, a lead introduction tool 380 (shown in FIG. 6A)includes substantially the same features and attributes as leadintroduction tool 350 of FIGS. 6A-6B, except for including a straightdistal portion 382 with a side opening 390 instead of the curved distalportion 372 and end opening 378 shown in FIG. 6A. Accordingly, in thisembodiment, straight distal portion 382 includes the side opening 390sized and shaped to facilitate passage of a distal portion of astimulation lead therethrough. In one aspect, opening 390 is configuredas a side-directed, non-coring opening for lumen 370. With thisarrangement, upon insertion percutaneously, the cannula body 360 of tool380 is oriented generally perpendicular relative to the skin andrelative to the hypoglossal nerve, with the distal side opening 390enabling a stimulation lead to exit cannula body 360 in a path extendingat a generally obtuse angle relative to the orientation of body 360 (asit percutaneously extends through a skin surface and tissues) andgenerally parallel to the hypoglossal nerve to be advanced generallyparallel to the hypoglossal nerve.

When using lead introduction tool 380, the distance D1 shown in FIG. 6Aand FIGS. 7C-7E is generally not tracked because of the straight shapeof distal portion 382 (including tip 384) and because the leadintroduction tool 380 is oriented generally perpendicular to thehypoglossal nerve over the optimal stimulation site. However, in oneaspect, one can optionally account for the length of the electrodeportion of a stimulation lead as it would extend generally outward andaway from the distal tip 384 through opening 390 (and generallyperpendicular to a longitudinal axis of the cannula body 360).Accordingly, in the embodiment of lead introduction tool 380, inaddition to identifying the optimal stimulation site (e.g. A in FIGS.7A-7E) with the site locator tool 200, the operator would also identifya skin entry point (e.g. G in FIG. 7C) that is spaced by the distance D2from the optimal stimulation site. The distance D2 generally correspondsto the length of the stimulation lead (including the electrode portion)that would extend out of distal side opening 390 to deliver theelectrode portion of the stimulation lead at the target stimulationsite. In this way, the operator insures that the electrode portion ofthe stimulation lead is accurately delivered to the identified targetstimulation site (e.g. A). As noted previously, the distance D2 wouldhave a length no more than, and likely less than, a length of theelectrode portion (such as electrode array 442 in FIG. 8B) to ensurecentering the electrode portion relative to the target stimulation site.

In some embodiments, the stimulation lead (e.g., stimulation lead 430 aswill be described in association with at least FIGS. 8A-8E) isconfigured to be cooperable with a removably attachable stylet tofacilitate advancing the stimulation lead through cannula 380 andthrough the tissue surrounding the target stimulation site. Inparticular, as the distal portion of the stimulation lead exits thedistal side opening 410, the distal portion 436 will have to be advancedvia tunneling through the surrounding tissue. With this in mind, thestylet will provide rigidity as the stimulation lead is tunneled to thetarget stimulation site and once the stimulation lead is properlypositioned, the stylet is removed from its connection to the stimulationlead. Moreover, in some embodiments, this stylet is also used toselectively deploy an anchoring mechanism associated with the electrodeportion of the stimulation lead.

In some embodiments, the cannula of lead introduction tool 350 or 380 isgenerally non-conductive and the conductive elements of the site locatortool 200 and/or of the stiffener are used as an electrically conductivepathway to confirm the location of the target stimulation site and/orthe location of the skin entry point spaced from the target stimulationsite.

In some embodiments, other types of introducing mechanisms are used toestablish a percutaneous access pathway for a stimulation lead. Forexample, one introducing mechanism includes a guide wire and a needlehaving a cannula and a stylet. With this arrangement, the needle cannulais percutaneously inserted to establish a percutaneous pathway with aidfrom the stylet to steer, guide, and/or stiffen the needle cannula.After a path is established by the combination of the cannula andstylet, the stylet is removed. With the cannula still in place, a guidewire is inserted into a proximal portion of the cannula and advancedthrough the cannula until a distal portion of the guide wire is adjacentthe target stimulation site. Next, with the guide wire still in place,the cannula portion of the needle is removed proximally over the guidewire, leaving just the guide wire in place. Using known techniques, astimulation lead is releasably coupled to the guide wire and advanced,via the guide wire, through the established percutaneous access pathwayuntil an electrode portion of the stimulation lead is adjacent thetarget stimulation site. With the stimulation lead remaining in place,the guide wire is then removed. Finally, the stimulation lead isanchored to maintain the electrode portion in an electrically coupledrelationship with the target stimulation site of the nerve.

While various different shapes and forms of leads can be used in themethods and systems of the present disclosure, FIGS. 8A-8C illustrateone exemplary embodiment of a stimulation lead 430 is that is configuredto be deployed percutaneously. In one embodiment, the stimulation lead430 is delivered via the tools 200, 350, 380 (as previously described inassociation with FIGS. 4-7) while in other embodiments, the stimulationlead 430 is delivered via other minimally invasive delivery techniques.Various aspects of the delivery of stimulation lead 430 will bedescribed herein in further detail.

As shown in FIGS. 8A-8C, stimulation lead 430 includes a front side 432and a back side 434 with the lead 430 extending between a distal portion436 and a proximal portion 438.

At distal portion 436, the front side 432 supports an electrode portion440 including a first array 442 of electrodes 444. In general terms,substantially the entire length of the electrode portion 440 comprises agenerally flat surface and when the back side 434 also forms a generallyflat surface, then the entire distal portion 436 defining the electrodeportion 440 comprises a generally flat or planar member (with theexception of the to-be-described protrusions 464 on back side 434).

This generally flat or planar configuration of distal portion 436(including stimulation electrode portion 440) provides a low profiletopography, thereby facilitating its advancement through the tissuesurrounding the hypoglossal nerve. In addition, by having at least agenerally flat surface of the front side 432 of distal portion 436, amuch closer and effective interface between the stimulation electrodeportion 440 and the surface of the hypoglossal nerve can be achieved.However, in some other embodiments, the front side 432 of the distalportion 436 is not generally flat, but has at least some curved portionor undulating portion. In one example, as illustrated in FIG. 8F, thecurved portion of the front side 432 of the distal portion 436 forms agenerally concave shape configured to accentuate the extent to which theelectrode portion 440 reciprocally conforms to the generally arcuateshape of the outer surface of the hypoglossal nerve. In another example,as illustrated in FIG. 8G, the front side 432 of the distal portion 436forms a generally convex shape. In one aspect, this generally convexshape is configured to accentuate slidable passage of the distal portionthrough the tissue surrounding the hypoglossal nerve to arrive at theoptimal stimulation site

Likewise, in some embodiments, the back side 434 of the distal portion436 is not generally flat, but has at least some curved portion whichcan be concave or convex. In one aspect, a generally convex shape on theback side 436 is configured to accentuate slidable passage of the distalportion through the tissue surrounding the hypoglossal nerve to arriveat the target stimulation site.

In another aspect, because the front side 432 carries electrode portion440, the back side 434 of the distal portion 436 is generally made orcoated with an electrically insulative material. With this arrangement,back side 434 effectively acts as a shield to prevent the stimulationsignal from affecting the sensory nerves and skin overlying thestimulation site.

In another aspect, at proximal portion 438 of stimulation lead 430, asecond array 450 of electrodes 452 is formed on both the front side 432and the back side 434 of stimulation lead 430. The first array 442 ofelectrodes 444 are electrically connected to the second array 450 ofelectrodes 452 with the second array 450 of electrodes 452 configured toprovide electrical connection to the IPG (55 in FIG. 1 or 109 in FIG.2). Via control from the IPG 55, each electrode 444 of stimulationelectrode portion 440 is independently programmable to apply astimulation signal that has a selectively controllable polarity,amplitude, frequency, pulse width, and/or duration.

In one embodiment, the first array 442 of electrodes 444 includes alateral component (i.e., extending along a width W1) or a longitudinalcomponent (i.e., extending along a length L1) of at least threeelectrodes in a guarded cathode electrode polarity arrangement. Thisguarded cathode electrode polarity arrangement hyperpolarizes tissuesnear the hypoglossal nerve while providing for complete depolarizationof the volume of the hypoglossal nerve adjacent the electrode portion440 of the stimulation lead 430. However, as shown in FIG. 8B, in someembodiments, the first array 442 includes a multitude of electrodes 444(substantially greater than three) extending along the width and alongthe length of the electrode portion 440. This arrangement permitsselection of different combinations of electrodes 444 from among thefirst array 442, thereby optimizing the stimulation of the hypoglossalnerve via an optimal combination of electrodes 444 within the firstarray 442. Moreover, in some embodiments, one or more of the electrodes444 are varied in shape and/or pitch, or varied by staggering of therows of electrodes 444.

In some embodiments, with the assumption that a diameter of the targetnerve in the region of the target stimulation site is about 3millimeters, the electrode portion 440 will have a width (W1 in FIG. 8B)of at least about 5 millimeters. Accordingly, in these embodiments, thewidth (W1) of the electrode portion 440 is at least substantially equalto or substantially greater than the diameter of the target nerve in theregion of the target stimulation site. This relationship insures thatthe electrical stimulation signal (for treating sleep apnea) will affectthe full cross-section of the nerve so that substantially all the axonsof the target nerve will potentially be activated (depending upon theparameters of the applied stimulation signal).

A body portion 437 extends between the electrode portion 440 (at thedistal portion 436) and the proximal portion 438. With the exception ofelectrodes 444, the body portion 437 is a generally insulative memberdevoid of electrodes on the front side 432 and back side 434. It isunderstood, of course, that wires extend through an interior of the bodyportion 437 to connect electrodes 444 to the IPG (55 in FIG. 1 or 109 inFIG. 2). In general terms, the body portion 437 has a length sufficientto extend from the electrode portion 440 to the IPG 55 (FIG. 1).

In some embodiments, the distal portion 436 of stimulation lead 430includes an anchoring mechanism 462 located on back side 434, i.e. on anopposite side relative to the stimulation electrode portion 440. In oneaspect, the anchoring mechanism 462 provides a cuff-less arrangement tosecure the electrode portion 440 in close proximity to the nerve withthe anchoring mechanism being disposed on an opposite side of theelectrode portion 440 so that the anchoring mechanism 462 faces awayfrom the nerve. This arrangement secures the electrode portionindependently of the nerve and in a desired position relative to thenerve without placing any pressure or other mechanical effects on thenerve that might otherwise be used to secure an electrode relative to anerve.

In one aspect, the anchoring mechanism 462 includes at least one arrayof protrusions 464. In one embodiment, the protrusions 464 are flapsformed of a resilient material while in other embodiments, theprotrusions 464 are barbs, prongs, or other anchoring components. Insome of these embodiments, the protrusions are sized and shaped toinduce fibrotic growth at and near the protrusions to cause furtheranchoring of the distal portion 436 of the stimulation lead 430. In oneaspect, within about one month, the protrusions 464 become ingrown withfibrotic tissue. Accordingly, while the protrusions 464 act to providesome long-term stability to the position of stimulation lead 430 withinthe body, one purpose of the protrusions 464 is to provide suchstability for at least about one month, which generally corresponds tothe amount of time for fibrotic tissue growth to effect a morepermanent, long term stabilization of electrode portion 440 at thetarget site within the body.

In one aspect, the protrusions 464 extend generally outward at an angle(e.g., 30, 45, 60 degrees) from a surface of the back side 434 of thedistal portion 436 of the stimulation lead 430. As shown in FIGS. 8A and8B, in some embodiments, at least one pair of the protrusions 464 areprovided in a divergent orientation which enhances the stability of thestimulation lead 430 by reducing the likelihood of the stimulation lead430 from migrating away from its placed location. In particular, onceimplanted, the divergent orientation of the protrusions 464 enhancemaintaining the electrode portion 440 of the stimulation lead 430 in itstarget location regardless of the direction of applied forces on thestimulation lead. In one aspect, the protrusions 464 have a length andwidth configured to engage or integrate with the tissues surrounding thehypoglossal nerve. However, in another aspect, the protrusions 464 forma generally tab-like structure made of a flexible polymer that cancollapse upon application of a sufficiently high force, thereby enablingadjustment of the position of the electrode portion 440 of thestimulation lead 430 and/or removal of the stimulation lead 430.

In some embodiments, the protrusions 464 are sized and shaped tofacilitate their disengagement from the surrounding tissues (via the useof a tool) to enable removal of the electrode portion 440 of thestimulation lead 430 from its implanted location adjacent thehypoglossal nerve. Such removal would take place in the event that atrial treatment plan was ineffective or in the event that thestimulation lead 430 was malfunctioning.

However, in the event that only some of the electrodes 444 weremalfunctioning, the stimulation lead 430 need not be removed because theIPG 55 of FIG. 1 (or IPG 109 in FIG. 2) can be used to activate adifferent set of electrodes 444 within the first array 442 to produce anew combination of electrodes 444 arranged to apply a therapeuticregimen for treating sleep apnea. Moreover, an adjustment of thestimulation parameters (e.g., amplitude, pulse width, frequency,duration, and electrode polarity) via the IPG 55, 109 can compensate forthe different position of the electrodes in the new combination ofactivated electrodes 444 for applying the stimulation signal. In thisembodiment, the many varied positions of the electrodes 444 both alongthe length of the distal portion 436 of the electrode portion 440 of thelead 430 and transversely across the distal portion 436 enables preciseactivation of selective groups of electrodes 444 (at their variousspaced apart locations) to produce an effective stimulation signal.Likewise, in the event that some inadvertent migration of thestimulation lead 430 occurs distally or proximally relative to theoptimal stimulation site after the stimulation lead 430 has beenconsidered to be properly placed, then the IPG 55 (or IPG 109 in FIG. 2)is used to activate a different set of electrodes 444 of the first array442 to achieve a stimulation signal that compensates for the migrationto maintain a proper stimulation signal at the target stimulation site.

The stimulation lead 430 is configured to balance various parametersincluding optimal electrode orientation, patient comfort, anchorstrength, preventing migration of the lead, and providing forremovability of the lead, as well as facilitating subcutaneous tunnelingof the stimulation lead 430 to the site of the IPG. As such, thisstimulation lead 430 provides several advantageous features, includingproviding for stimulation of the entire cross-sectional volume of thehypoglossal nerve volume in a manner comparable with cuff electrodes.Moreover, by facing the electrodes 444 away from the skin and by backingthe electrodes 444 with an insulative layer (body portion 437), thestimulation lead 430 minimizes stimulation of nearby sensory nerves. Inaddition, by having an array 442 of multiple electrodes 444 that areindependently programmable or controllable relative to each other viaoperation of IPG 55, the therapy can be adjusted in a non-invasivemanner in the event that the stimulation lead 430 migrates from itsoriginal placement. In other words, the stimulation can be shifted fromone combination of electrodes 444 in the array 442 to a differentcombination of electrodes 444 in the array 442 to account for the shiftin the overall position of the electrode portion 440 of the stimulationlead 430 relative to the hypoglossal nerve. Of course, it will beunderstood that different combinations of electrodes 444 can beactivated simply to achieve a different therapy regimen, even in theabsence of migration or malfunction of electrode array 442.

In use, the stimulation lead 430 is delivered percutaneously via feedingthe distal portion 436 into a proximal portion 369 of the cannula 360 oflead introduction tool 350 or 380 and slidably advancing the distalportion 436 therethrough until the distal portion 436 of stimulationlead 430 exits the distal opening (390 or 410, respectively) of the leadintroduction tool 350, 380 to be oriented generally parallel and closelyadjacent to the hypoglossal nerve at a target stimulation site (e.g. A)with the electrode portion 440 facing toward the nerve and away from theskin (and underlying sensory nerves), as illustrated in FIG. 7D. Next,while maintaining the position of the distal portion 422 (e.g. electrodearray 442 in FIG. 8B) stimulation lead 430, the tool 350 is withdrawnproximally from tissues 404, 405 to leave just stimulation lead 430 inplace, as illustrated in FIG. 7E. From this configuration, the proximalportion 421 of stimulation lead 430 is tunneled and/or maneuveredsubcutaneously to extend from the neck region to a pectoral region, toachieve a general configuration similar to that shown in FIG. 1 for lead52.

In some embodiments, as shown in perspective view of FIG. 8D and thesectional view of FIG. 8E, a distal tip 364A of a lead introduction tool350A includes a shell-like cover 480 protruding distally outward fromthe cannula body 360A and is configured with a wall 482 to control thedeployment of the protrusions 464 of the anchoring mechanism 462 ofstimulation lead 430. In particular, the wall 482 of cover 480 acts as abarrier to maintain the protrusions 464 in a collapsed position againstor close too the back side 434 of the distal portion 436 of thestimulation lead 430 so that the protrusions 464 do not engage thesurrounding tissue prior to proper positioning of the stimulationelectrode portion 440 against the hypoglossal nerve. At the same time,the distal portion 364 continues to define an opening 365A generallyopposite the cover 480 to enable exposing the electrode array 442 to thetarget nerve to allow testing or confirming positioning over the targetstimulation site prior to deploying the anchor mechanism 462. In someembodiments, the cover 480 defines a half-circular cross-sectional shapehaving a diameter (D3) generally corresponding to a diameter of cannula360. Once proper positioning of the stimulation electrode 440 has beenachieved and upon proximally withdrawing the tool 350A, the cover 480 iswithdrawn from its position over anchoring mechanism 462, therebyreleasing protrusions to engage surrounding tissues. Likewise, in theevent that the stimulation lead 430 must be removed, the cover 480 ofthe lead introduction tool 350 will force the collapse of theprotrusions 464 (against the body of the distal portion 436 of thestimulation lead 430) as the distal portion 436 of the stimulation lead430 is withdrawn proximally into the lead introduction tool 350A.

In another aspect, once implanted, a stimulation system forautomatically treating obstructive sleep apnea will preferably remain ina stable position to endure the normal activities of the patient. Forexample, the neck of a patient moves through a wide range of motionthrough many different positions. To counteract the potential for astimulation lead to move back and forth along the hypoglossal nerve(relative to a desired stimulation site), the anchoring mechanism 462anchors the distal portion 436 of the stimulation lead 430 at the targetstimulation site of the nerve. Accordingly, this anchoring mechanisminsures that proper placement of the stimulation lead is maintaineddespite the dynamic motion and varying positions of the neck, whichcould otherwise cause inadvertent repositioning of the stimulation lead(relative to the target nerve) if the distal anchoring mechanisms werenot present.

In addition, as previously noted, the anchoring mechanism 462 maintainsthis stable position without encircling the nerve (as a conventionalcuff would) via an anchoring mechanism located on a directly oppositeside of the distal portion 436 of the stimulation lead 430 with theanchoring mechanism 462 engaging the surrounding tissue instead ofengaging the nerve. Nevertheless, to the extent that the electrodeportion 440 of the distal portion 436 remains in close proximity orcontact with the nerve, this relationship also contributes to thestability of the distal portion 436 because the anchoring mechanism 462(on the opposite side from the electrode portion 440) is simultaneouslysecuring the distal portion 436 in its desired position.

Accordingly, in some embodiments, as shown in FIG. 9, a second anchoringmechanism 502 and/or third anchoring mechanism 504 is deployed tofurther stabilize the position of the stimulation lead 430 in additionto the first anchoring mechanism 462. As shown in FIG. 9, body portion437 of stimulation lead 430 extends proximally from the electrodeportion 440 and from the first anchoring mechanism 462 while the secondanchoring mechanism 502 is positioned at a first distance (D3) away fromthe first anchoring mechanism 462. The third anchoring mechanism 504 isspaced proximally by a second distance (D4) from the second anchoringmechanism 502. As further shown in FIG. 9, a first region 510 (includingportion 437) of simulation lead 430 extends between first anchoringmechanism 462 and second anchoring mechanism 502 while a second region512 extends between second anchoring mechanism 502 and third anchoringmechanism 504. Finally, a third region 514 of lead 430 extendsproximally from third anchoring mechanism 504 for passage toward the IPG(55 in FIG. 1 or 109 in FIG. 2).

In some embodiments, both the first region 510 and the second region 512of the lead body 437 are pre-shaped into a serpentine or S-shapedconfiguration prior to deployment. In this pre-shaped configuration,first region 510 has a first length (D3) while second region 512 has asecond length (D4). Once deployed via tunneling subcutaneously in apathway proximally from the stimulation site, the S-shaped first andsecond regions 510, 512 provide strain relief mechanisms that act inconcert with the first, second, and third anchoring mechanisms 462, 502,504 to stabilize the position of the stimulation lead 430 whilecompensating for movements of the body as described above.

FIG. 10 is a side plan view of a stimulation lead including a dynamicanchoring system 525, according to an embodiment of the presentdisclosure. As shown in FIG. 10, system 525 includes a first anchor 530,second anchor 532, and a third anchor 534 with portions 510 and 512 of astimulation lead interposed between the respective anchors. In oneembodiment, one, two, or three of the anchors 530, 532, 534 include abiomediating mechanism, that is, a mechanism to induce fibrotic growthin the surrounding tissue at which the respective anchor is located andthereby further anchor the distal portion of a stimulation lead. Asshown at 540 in FIG. 10, the anchors 530-534 comprise one or more oftines, mesh (e.g. Dacron mesh), barbs, flaps, and the like that areconfigured to mechanically engage the surrounding tissue.

In addition, in some embodiments, one or more of the anchors 530, 532,534 are configured to provide a surface sized or treated (coated) toinduce fibrotic growth to further secure the anchor. The “biomediating”anchors are particularly advantageous in a method of percutaneousdelivery because the anchors do not require suturing, and therefore,regions 514, 512, and 510 of the stimulation lead can be tunneled towardthe IPG 55 in FIG. 1 (or IPG 109 FIG. 2) without having to apply sutureswhen the anchors 530, 532, 534 arrive at their intended positions.However, it is understood that in some embodiments, minimally invasivesuturing techniques can be applied as desired to further secure therespective anchors in place (during the initial period of fibroticgrowth) to supplement the securing strength of the mechanical component(e.g., barbs, flaps, etc.) of the respective anchors.

FIGS. 11-14 schematically illustrate a method 550 of percutaneouslydelivering an electrode portion of a stimulation lead to a target nerve,according to an embodiment of the present disclosure. In viewing theFIGS. 11-14, it will be understood that sizes and/or relative spacing ofvarious components of the anatomy (e.g., a size or width of incision,nerves, muscles, skin layer, etc.) and/or components of the tools (e.g.,barbs, rods, etc.) have been exaggerated for illustrative clarity tohighlight application of the tool. This method achieves placement of theelectrode portion without the generally disruptive, and more timeconsuming, conventional cut-down implantation procedure (which wouldtypically include a full dissection around the target nerve). Moreover,it is understood that prior to deployment of method 550, one or moreoptimal stimulation sites on the hypoglossal nerve have been identifiedvia a site locator tool (e.g. site locator tool 200) or via other tools.It is also understood that one or more surgical navigation techniquesare used to: (1) employ the site locator tool to identify the optimalstimulation site; (2) make an incision to provide a skin entry pointgenerally over the optimal stimulation site; and (3) guide the distalportion of an introduction tool or implantation instrument to thatoptimal stimulation site.

As shown in FIG. 11, method 550 includes making an incision 553 throughthe skin 552 and through first muscle layer 554 to provide access to thepreviously identified optimal stimulation site at target nerve 558, suchas the hypoglossal nerve. The incision is relatively small, such as 2centimeters wide, so that the access to the nerve 558 is consideredminimally invasive. Next, via use of an implantation instrument 560, anelectrode portion 565 of a stimulation lead 568 is inserted through theincision 553 and guided to the nerve 558. As shown in FIG. 12, theimplantation instrument 560 includes a distal tip 562 from which aselectively deployable, engagement mechanism 570 protrudes and a barrel563 extending proximally between a handle 564 and distal tip 562. Thebarrel 563 is configured to support deployment of the engagementmechanism 570. A trigger 561 mounted at handle 564 is connected to aproximal end of the engagement mechanism 570 and controls selectivedeployment of the engagement mechanism 570.

Moreover, in one embodiment, as shown in FIG. 13, the electrode portion565 comprises an insulative carrier 580 supporting an array of spacedapart electrodes 582 aligned in series. The carrier 580 also includes anarray of securing elements 584A, 584B, 584C, 584D extending outward fromthe sides and/or ends of the carrier 580 to facilitate securing thecarrier 580 relative to the surrounding tissues adjacent the hypoglossalnerve. The securing elements 584A-584D can be loops or any otherstructure to which a suture or fastener is securable relative to thesurrounding tissue. In this way, the electrodes 582 of the electrodeportion 565 become secured relative to nerve 558 with the electrodes 582facing the nerve 558. In one embodiment, the electrodes 582 are alignedwith a longitudinal axis of the electrode portion 565 and/or of thestimulation lead supporting the electrode portion 565. As previouslynoted, the electrode portion 565 is implanted so that the electrodes 582also face away from the skin 552 (with carrier 580 acting as a shield)to minimize stimulation of sensory nerves at or near the skin 552.

In one aspect, as shown in FIG. 13, the electrodes 582 have a width W2(at least 3-5 millimeters) generally equal to or greater than a diameterof the target nerve (e.g., 3 millimeters) while carrier 580 has a width(W3) substantially greater than the width W2 of the electrodes 582 toinsure shielding of the skin from the stimulation signal emitted fromelectrodes 582.

Referring again to FIG. 11, once the electrode portion 565 is properlypositioned over the nerve 558, the implantation instrument 560 securesthe electrode portion 565 in position relative to the nerve 558 viaengagement mechanism 570. While the engagement mechanism 570 can takemany different forms, in one embodiment shown in FIG. 14, the anchoringmechanism 570 protrudes from the distal portion 562 of barrel 563 ofimplantation instrument 560.

In particular, the anchoring mechanism 570 includes one or more smalldiameter rods 572 extending longitudinally within a conduit formed bybarrel 563 with each rod 572 supporting a needle 574 configured toselectively extend distally from an end of each respective rod 572. Inone embodiment, barrel 563 includes a generally hollow, elongate tubularmember, and the rods 572 extend through a length of the barrel 563 whilebeing longitudinally movable within the barrel 563.

Each needle 574 includes a barb 576 removably mounted at a distal end575 of the needle 574. In one embodiment, barbs 576 are made from astainless steel material or a plastic material while having a relativelysmall length and/or diameter (e.g., 1-3 millimeters) to avoid patientdiscomfort. In addition, a suture 575 includes a first end connected tothe barb 576 and a second end connected to securing elements 584 ofelectrode portion 565 of the stimulation lead. In a pre-deploymentstate, the respective sutures 575 are in a relaxed state withouttension. In one embodiment, needles 574 are formed of a metal, such as aNitonol material.

Accordingly, with the electrode portion 565 positioned over an optimalstimulation site of the nerve 558, trigger 561 activates anchoringmechanism 570 to automatically cause the rods 572 to force the needles574 to protrude distally outward and penetrate into surrounding tissuesadjacent the nerve 558 and electrode portion 565, and then the trigger561 is subsequently relaxed causing retraction of rods 572 and theirrespective needles 574. However, the barbs 576 remain fixed in thesurrounding tissues because they detach from the needles 574 (at a pointof detachment represented by dashed lines 579) as the needles 574 areretracted. At this point, the implantation instrument 560 is removedfrom the incision site, leaving the electrode portion 565 in place.

In one aspect, as the needles 574 are advanced to place the barbs 576into the tissue the sutures 575 become under tension, and as the needles574 are retracted into barrel 563 with the barbs 576 remaining in thetissue, the sutures 575 remain under tension which effectively exertstension on the carrier 580 to urge electrodes 582 into pressing contactagainst the nerve. For example, as schematically illustrated in the sideview of FIG. 14B, with barbs 576 deployed in tissue 590, securingelements 584B, 584D (and their respective sutures 575) are undertension, thereby urging electrode portion 565 (and particularlyelectrodes 582) against the nerve 592. This arrangement provideslongitudinal stability to the secured position of the electrode portion565 relative to the nerve. While not shown it is understood that thesecuring elements 584A, 584C on the opposite side of the electrodeportion 565 also would be deployed via sutures 575 and barbs 576 so thatall four securing elements 584A, 584B, 584C, 584D of electrode portion565 are deployed. Accordingly, when secured under tension relative tothe tissue 592 (via sutures 575 and barbs 576), securing elements 584Aand 584C also provide longitudinal stability to the position of theelectrode portion 565 relative to the nerve 590.

Moreover, in such an arrangement, securing element 584A and securingelement 584B are positioned on opposite sides of the electrodes 582 tostraddle the nerve 592, thereby insuring lateral stability of theelectrode portion 565. Likewise, securing element 584C and securingelement 584D are positioned on opposite sides of the electrodes 582 tostraddle the nerve 592, thereby insuring lateral stability of theelectrode portion 565.

In some embodiments, as shown in FIG. 14B, the securing elements 584 aremade of a flexible material to permit their bending toward the tissue tofacilitate securing the barbs 576 and sutures 575 under tension. Inthese embodiments, the carrier 580 supporting the securing elements 584can be either substantially rigid as shown in FIG. 14B or can begenerally flexible as shown in FIG. 14C. In particular, as shown in theschematic sectional view of FIG. 14C, an electrode portion 565 includesa flexible carrier 581 supporting electrodes 582 with the carrier 581configured to flexibly conform to the arcuate shape of the cross-sectionof the nerve 558. This arrangement insures close contact of theelectrode 582 relative to the nerve 558 and accentuates the applicationof tension on sutures 575 when barbs 576 are anchored into thesurrounding tissue 590. In another aspect, it will be clear from aconsideration of both FIGS. 14B and 14C, the securing elements include afirst array of barbs for deployment on one side of the electrode portion565 and a second array of barbs for deployment on an opposite side ofelectrode portion 565.

After securing the electrode portion 565, the implantation instrument560 is removed and the lead body 567 of the stimulation lead 568 isdelivered subcutaneously, via a tunneling tool, from the anchored siteof the electrode portion 565 to the IPG 55 (FIG. 1).

Various configurations of stimulation electrode portions of astimulation lead are described and illustrated in association with theembodiments of FIGS. 15-27. These various stimulation electrode portionscan be delivered percutaneously or via other suitable deliverytechniques. In some embodiments, the electrode portions and/orsupporting proximal portions of the stimulation lead are configured tohave a minimal mechanical impact on the nerve and the surroundingtissues and/or are configured to be implanted via minimally invasivetechniques.

FIGS. 15-17B schematically illustrate stimulation system including abio-absorbable electrode portion 601 of a stimulation lead 600,according to an embodiment of the present disclosure. It is understoodthat prior to deployment of electrode portion 600, one or more optimalstimulation sites on the hypoglossal nerve have been identified via asite locator tool (e.g. site locator tool 200 shown in FIG. 3) or viaother tools. It is also understood that one or more surgical navigationtechniques are used to: (1) employ the site locator tool to identify theoptimal stimulation site; and (2) place the electrode portion at thatoptimal stimulation site.

As shown in FIG. 15, stimulation lead 600 comprises an electrode portion601 including cuff 602 and electrodes 610, as well as wires 612, anchor614, and non-absorbable portion 620 of stimulation lead 600. In oneembodiment, the cuff 602 comprises a generally elongate tubular memberthat carries electrodes 610 and is configured to wrap around nerve 625in a releasably secured manner with a generally cylindrical shape,thereby maintaining electrodes 610 in close contact against nerve 625. Awire 612 extends proximally through the cuff 602 from each of therespective electrodes 610 and has a length extending further to anchor614 and non-absorbable portion 620 so that the wires 612 are inelectrical communication with IPG 55 (FIG. 1).

In some embodiments, as shown in FIG. 17A, each electrode 610 includes aconductive contact portion 616 and an electrically insulative cover 618.The electrically insulative cover 618 extends over the top portion 639of the contact portion 616, extends beyond all four sides of contactportion 616, including sides 635, 637 viewable in FIG. 17A. At aproximal end 634 of the electrode 610, a strain relief member 636connects wire 612 to contact portion 616 via wire 611. In oneembodiment, electrodes 610 are embedded in the cuff 602 with bottomportion 638 exposed at inner surface of cuff 602. In some embodiments,electrodes 610 are aligned such that a longitudinal axis of eachelectrode 610 is generally perpendicular to a longitudinal axis of thecuff 602 and the respective electrode 610 are spaced apart from eachother along a length of the cuff 610.

In one aspect, cuff 602 is made of a bio-absorbable material so thatover a period of several weeks following the implantation of electrodeportion 601, the cuff 602 is absorbed by the body, thereby leaving theelectrodes 610 in their desired position relative to nerve 625. At thesame time that the cuff 602 is being absorbed, tissue growth occurs atand around the wires 612 and occurs at and around the electrodes 610 asthey become exposed from absorption of cuff 602. In some embodiments,wires 612 are arranged with several coiled portions 613 (highlighted inthe enlarged caption in FIG. 15) to further induce fibrotic tissuegrowth at and around the wires 612 such that tissue growth at eachcoiled portion acts as a separate anchor.

After the absorption process for cuff 602 (and any other bio-absorbablecomponents) is complete, the fibrotic tissue growth is sufficient to actas an anchoring mechanism to maintain the position of the electrodes 610in their generally spaced apart relationship at the intended stimulationsite and to secure the wires 612 to further maintain the position ofelectrodes 610. The resulting arrangement is illustrated in FIGS. 16 andFIG. 17B. In the sectional view of FIG. 17B, fibrotic tissue growth 642surrounds the electrode 610 and wires 612 to mechanically secure theelectrodes 610 in position over nerve 625 beneath skin/muscle portion640. As further shown in FIG. 17B, insulative cover 618 protects eachelectrode 610 from the tissue growth 642. In one aspect, the insulativecover 618 covers a top portion and sides of each electrode 610 while abottom portion of each electrode element 610 remains exposed to nerve625. In some embodiments, the outer surface of insulative cover 618includes a coating configured to induce the fibrotic tissue growth.

In one aspect, by employing a bio-absorbable cuff and inducing tissuegrowth to secure electrodes 610, this system provides minimal long-termimpact at the implantation site. In particular, the implanted, cuff-lessset of electrodes 610 will be comfortable for the patient because of theabsence of the relatively bulky size of a conventional cuff. Thiscuff-less arrangement also will be less likely to induce inadvertentmechanical effects on the target nerve (as compared to a conventionalcuff electrode system), which can affect nerve function and comfort.

In some embodiments, anchor 614 is also made of bio-absorbable materialand is absorbed over time within the body. Accordingly, tissue growthalso would occur in this region to further secure wires 612 in place.

However, in some embodiments, as shown in FIGS. 15-16, the stimulationlead 600 includes a non-absorbable fastener 622 configured to maintainthe separate wires 612 in a grouped arrangement. In one aspect, fastener622 insures an orderly transition of the separate wires 622 to thepermanent lead portion 620 that extends to the IPG 55 (FIG. 1). Inanother aspect, fastener 622 also provides strain relief to preventinadvertent pulling of wires 612 on the target nerve. However, in otherembodiments, this fastener 622 is omitted or is made of a bio-absorbablematerial.

FIGS. 18-21 schematically illustrate a bio-absorbable electrode portion650 of a stimulation lead, according to an embodiment of the presentdisclosure. It is understood that prior to deployment of electrodeportion 650, one or more optimal stimulation sites on the hypoglossalnerve have been identified via a site locator tool (e.g. site locatortool 200) or via other tools. It is also understood that one or moresurgical navigation techniques are used to: (1) employ the site locatortool to identify the optimal stimulation site; and (2) place theelectrode portion at that optimal stimulation site. Finally, it is alsounderstood that the electrodes 660 of electrode portion 650 would beelectrically connected via wires and a lead body to an IPG 55 (FIG. 1)and that this general arrangement is omitted in FIGS. 18-21 forillustrative clarity.

FIGS. 18-19 are plan views of an electrode portion 650 of a stimulationlead in which the electrode portion 650 includes a generally flexiblecoil member 651 and electrodes 660. In general terms, the coil member651 wraps around a nerve 663 and defines a stent-like insulative memberthat maintains electrodes 660 in close contact against nerve 663.However, unlike a conventional cardiovascular stent which is deployedwithin a blood vessel via expanding the stent outward against the wallof the blood vessel, the coil member 651 is configured to wrap around anouter surface of a nerve 663 in a self-sizing relationship and is notconfigured to expand radially when deployed in the desired position.

In some embodiments, the coil member 651 forms a generally helical shapeand includes a pair of spaced apart rails 652 with numerous struts 654extending between and interconnecting the rails 652. In one embodiment,the rails 652 and struts 654 are made of non-conductive materials. Inone aspect, electrodes 660 are sized and shaped to extend between a pairof rails 652, as shown in FIGS. 18-19, in a manner similar to the struts654. In one embodiment, the electrodes 660 are in general alignment witha longitudinal axis of the coil member 651. However, it will beunderstood that the coil member 651 is not strictly limited to thearrangement of rails 652 and struts 654 shown in FIGS. 18-19 becausenumerous variations and arrangements of struts can be used to form thehelically shaped coil member.

As shown in its pre-deployment state in FIG. 18, coil member 651 has aninner diameter (D6) that is substantially less than a diameter (D5) ofthe target nerve 663 (see also FIG. 19). Accordingly, when coil member651 is placed about the larger diameter nerve 663, the coil member 651wraps about the nerve 663 in a self-sizing manner such that the innerdiameter of the coil member 651 substantially matches the diameter ofthe target nerve 663, as shown in FIG. 19. To the extent that anyspacing is shown between the coil member 651 and nerve 663 in FIG. 19,this spacing is provided for illustrative clarity to clearly define thecomponents of the coil member 651 separately from nerve 663.

In some embodiments, the coil member 651 attracts tissue growth at rails652 and struts 654 with the combination of the tissue growth and therails 652 and struts 654 acting as an anchoring mechanism to maintainthe electrodes 660 in close contact against nerve 663.

In some other embodiments, the coil member 651 forms a bio-absorbablematerial so that after absorption of rails 652 and struts 654 takesplace, electrodes 660 remain in close contact to nerve 663 with tissuegrowth 670 on and around the electrodes 660 holding the electrodes 660in place relative to the nerve 663, as shown in FIGS. 20-21. The variouscomponents (struts and rails) of the coil member 651 form a latticeworkor frame configured to induce fibrotic tissue growth in a patterngenerally matching the structure of the coil member 651 so that theinduced tissue growth forms in a mechanically advantageous frameworkholding the electrodes 660 in place relative to the nerve 663. In oneaspect, this framework of fibrotic growth forms a bio-cuff in whichtissues produced within the body form a cuff to maintain the electrodes610 in the desired position relative to the nerve.

It is understood that tissue growth also would occur at and around thewires (not shown) extending proximally from the electrodes 660 towardthe IPG 55 (FIG. 1). It is further understood, that similar to previousembodiments, an outer portion of the electrode 660 (the portion thatdoes not contact the nerve 663) would include an insulative cover to actas a barrier between the contact portion of the electrode 660 and thesurrounding tissue.

Moreover, in one embodiment, each electrode 660 is connected to arespective one of an array of wires with each respective wire connectedto, and extending to, a stimulation lead body configured for electricalcommunication with an IPG 55 (FIG. 1). In one embodiment, the array ofwires includes substantially the same features and attributes as thearray of wires 612, as previously described and illustrated inassociation with FIGS. 15-16.

FIGS. 22-24 schematically illustrate an electrode portion 700 of astimulation lead, according to an embodiment of the present disclosure.It is understood that prior to deployment of electrode portion 700, oneor more potential stimulation sites on the hypoglossal nerve have beenidentified via a site locator tool (e.g. site locator tool 200) or viaother tools. It is also understood that one or more surgical navigationtechniques are used to: (1) employ the site locator tool to identify theoptimal stimulation site; and (2) place the electrode portion at thatoptimal stimulation site.

As shown in FIGS. 22-23, electrode portion 700 includes a carrier 702supporting generally spike-shaped electrodes 710 that are spaced apartfrom each other along a length of the carrier 702. The carrier 702includes a distal end 704 and a proximal end 706 while each electrode710 forms a conductive member including an exposed distal tip 714 and aninsulative covered base portion 712. While just two electrodes 710 areshown, it will be understood that in other embodiments, carrier 702supports more than two electrodes 710. In one embodiment, the carrier702 comprises a generally flat member having a first side and a secondside (opposite the first side), with the electrodes 710 extendinggenerally outward from the first side of the generally flat member.

In another aspect, for each electrode 710, a separate wire 720 extendsthrough the carrier 704 (shown as dashed lines in FIG. 23) and iselectrically connected to the base portion 712 of each respectiveelectrode 710. It is further understood that the electrodes 710 areformed of ultra fine wires, as known to those skilled in the art, andthat the electrodes 710 are shown in FIGS. 22-24 in an exaggerated,enlarged form strictly for illustrative purposes.

Once the electrode portion 700 is delivered to the intended stimulationsite, pressure is applied to insert the distal tips 714 of therespective electrodes 710 into the nerve 730. Because of the smalldimensions of the ultra fine wire forming each electrode 710, theelectrodes 710 are maintained in this position via the tissue of thenerve effectively capturing the electrodes 710. With this arrangement,close contact of the electrodes 710 to the nerve 730 is insured,resulting in effective stimulation of the nerve 730.

In some embodiments, once the electrode portion 700 is secured in place,the electrode portion 700 attracts tissue growth (not shown) aboutcarrier 702 and base portion 712 of needles 710 with the combination ofthe tissue growth and the carrier 702 and base portions 712 acting as ananchoring mechanism to maintain the electrode tips 714 in penetratingengagement (i.e. inserted engagement) relative to nerve 730.

In some other embodiments, the carrier 702 forms a bio-absorbablematerial so that carrier 702 is absorbed over time, leaving justelectrodes 710 and wire portions 721, 720 in place at nerve 730, asshown in FIG. 24. As the absorption of carrier 702 occurs, electrodes710 are held in inserted engagement relative to nerve 730 because oftissue growth (not shown) forming on and around the base portion 712 ofelectrodes 710 (as the carrier is absorbed) to hold the electrodes 710in penetrating engagement relative to the nerve 730. It is understoodthat a similar tissue growth would occur at and around the wire portions721 and 720 extending proximally from the electrodes 660 toward the IPG55 (FIG. 1).

FIGS. 25-32 schematically illustrate stimulation system 800 and a methodof implanting components of system 800, according to an embodiment ofthe present disclosure. As shown in FIGS. 25-27, the stimulation system800 includes at least an electrode portion 801 of a stimulation lead 802and a shield 804. It is understood that prior to deployment of electrodeportion 801, one or more optimal stimulation sites on the hypoglossalnerve have been identified via a site locator tool (e.g. site locatortool 200 shown in FIG. 1) or via other tools. It is also understood thatone or more surgical navigation techniques are used to: (1) employ thesite locator tool to identify the optimal stimulation site; and (2)place the electrode portion at that optimal stimulation site.

As shown in FIG. 25, stimulation lead 803 includes electrode portion 801and lead body 808 with the electrode portion 801 including a generallyelongate carrier body extending between a distal end 817 and a proximalend 816, and an electrode strip 815, which includes an array 818 ofelectrodes 820 spaced apart along a length of the carrier body. The leadbody 808 extends proximally from electrode portion 801 and includes ananchor 810 with a proximal lead portion 812 configured for extension toand electrical connection to an IPG (55 in FIG. 1 or 109 in FIG. 2).

The electrode strip 815 has a length (L2) substantially greater than adiameter of a nerve, and sufficient to extend across a diameter of anerve 840 and outward from both sides of the nerve 840, as shown in atleast FIGS. 26-27. In one embodiment, the length (L2) is at least twicethe diameter of the nerve. In another embodiments, the length (L2) is atleast three times the diameter of the nerve, such that with an expectednerve diameter of about 3 millimeters, the electrode strip 815 has alength (L2) of about 9 millimeters. In this embodiment, about 3millimeters of the full length of the electrode strip 815 would be inclose proximity or contact with the nerve 840 while about 3 millimetersof the length of the electrode strip 815 would extend outward from eachside of the nerve 840, as schematically illustrated in FIGS. 26-27. Insome embodiments, electrode strip 840 has a width (W4) of about 3millimeter, which facilitates a minimally invasive implantation methodin some embodiments (as will be later described in more detail inassociation with FIGS. 30-32). In comparison, a conventional cuffelectrode might typically have a width of about 9 millimeters.

In use, the electrode portion 801 is delivered to an intendedstimulation site along the hypoglossal nerve 840 and with the electrodestrip 815 having a generally perpendicular orientation relative to alongitudinal axis (represented by line A) of the nerve 840 (in theregion of the intended stimulation site), as shown in FIG. 26. In oneembodiment, as illustrated in the sectional view of FIG. 27, theelectrode portion 801 is positioned so that the electrodes 820 ofelectrode strip 815 faces toward nerve 840 to apply the stimulationsignal onto the nerve 840. Moreover, in some embodiments, each electrode582 is independently programmable or controllable via IPG 55 (FIG. 1) ina manner substantially similar to previously described embodiments toallow control and adjustment over the stimulation signal withoutre-positioning the electrode strip 815. In addition, an insulativeshield 804 is interposed between the nerve 840 and skin 830 (andunderlying muscle 832) such that the shield 804 permits application ofthe stimulation signal on the nerve 840 while preventing application ofthe stimulation signal on the skin 830.

In this arrangement, nerve 840 is sandwiched between the electrode strip815 and insulative shield 804 and the electrode portion 801 is deployedso that at least a portion of the electrode strip 806 extends, in closeproximity to or in close contact with, about the outer surface of thenerve 840, as shown in the sectional view of FIG. 27. However, in thissandwiched arrangement, each of the electrode strip 815 and shield 804are secured independently relative to the surrounding tissue such thatneither electrode strip 815 nor shield 804 are secured to the nerve 840.For example, in one embodiment, electrode strip 815 is secured at eachof its ends, via anchors (represented by x 878 and x 879 in FIG. 26),relative to the surrounding tissue and independent of nerve 840. Withthe generally perpendicular orientation of both the electrode strip 815and the shield 804, this configuration permits movement of the nerve 840in a lateral direction (represented by arrow M) relative to both theelectrode strip 815 and the shield 804, thereby accommodating shiftingof the nerve 840 as the neck of the patient moves through a wide rangeof motion through many different positions.

With this in mind, upon lateral movement of nerve (along arrow M), boththe electrode strip 815 and shield 804 remain stationary such that thesandwiched arrangement is maintained even when nerve 840 moves.Accordingly, because of the electrode strip 815 has a length (L2) thatis substantially longer than the diameter of nerve 840, in any lateralposition of the nerve 840 (within a natural, limited range of motion)the electrode strip 815 remains in a position to apply an efficaciousstimulation signal to nerve 840. Similarly, because the shield 804 haslength (L3) substantially longer than the diameter of nerve 840 andsubstantially longer than the length (L2) of the electrode strip 815,the shield is always positioned to block application of the stimulationsignal to the skin 830 (and underlying sensory nerves). In oneembodiment, shield 804 defines an area substantially greater than anarea of an electrical field produced by electrodes 820 toward a skinsurface.

While the electrode portion 801 extends generally perpendicular to thelongitudinal axis of the nerve 840 (at the stimulation site), in someembodiments the lead body 808 extends generally parallel to thelongitudinal axis of the nerve 840 to follow a path toward the IPG 55(FIG. 1). As previously noted, the lead body 808 includes an anchor 810to permit securely anchoring the lead body 808 (and therefore theelectrode portion 801 as well) relative to the anatomical structures andtissues nearby to the nerve 840. From the anchor 810, a proximal portion812 of the lead body 808 extends further toward the IPG 55 (FIG. 1) viaa subcutaneous tunnel.

In some embodiments, the application of a perpendicular orientation ofan electrode strip (e.g. electrode strip 815) relative to nerve 840 isused with other cuff-less electrode configurations. For example,embodiments associated with FIGS. 11-14C can be deployed to orient theelectrode portion 565 to be generally perpendicular to the nerve suchthat the series of electrodes 582 are aligned transverse to alongitudinal axis of the target nerve without a cuff encircling thecircumference of the nerve 840. It will be understood that the number ofelectrode contacts will be adjusted, as appropriate, in the electrodeportion 565 to insure capture of the nerve throughout a fullcross-section (or diameter) of the nerve.

In further reference to FIGS. 25-29, in some embodiments, electrodeportion 801 includes one or more anchoring mechanisms. Accordingly, FIG.28 is a top plan view of an electrode portion 850 including a series ofelectrode contacts 820, a distal end 852, and a proximal end 854. Atdistal end 852, one or more loops (or other securing elements) 860 areprovided to enable suturing or otherwise fastening the distal end 852relative to surrounding tissue adjacent the nerve 840. Similarly, atproximal end 854, one or more loops (or other securing elements) 870,872 are provided to enable suturing or otherwise fastening the proximalend 854 relative to surrounding tissue adjacent the nerve 840. In thisway, the electrode strip 850 is securable in a stable position close tonerve 840 (but independently of the nerve) without being secured to thenerve 840 itself and/or without encircling the nerve 840.

In some other embodiments, as schematically illustrated in the sectionalview of FIG. 29, electrode strip 815 and shield 804 are securedtogether. In these embodiments, the sandwiched configuration ofelectrode strip 815 and shield 804 is maintained relative to nerve 840to thereby permit lateral movement (directional arrow M) of nerve 840while still providing electrical stimulation of nerve 840 via electrodestrip 815 and while still protecting skin 830 via shield 804. Inparticular, fastening mechanism 870 includes a first component 872 and asecond component 874, with each respective component 872, 874 sized toextend between the electrode strip 815 and the shield 804. In onenon-limiting aspect, by providing first component 872 on one lateralside of nerve 840 (connected to the first ends of the respective stripand shield) and by providing second component 874 on an opposite lateralside of nerve 840 (connected to the second ends of the respective stripand shield), the fastening mechanism 870 provides a lateral boundary orbarrier to insure that nerve 840 will remain between electrode strip 815and shield 804 while permitting lateral movement of nerve 840. In otherembodiments, only one end of the respective electrode strip 815 and theshield 804 are secured together, leaving the other end open.

In one embodiment, the first component 872 of securing mechanism 870comprises a buckle-belt mechanism that is connectable to the distal end817 of electrode strip 815 and connectable to the distal end 805 of theshield 804. Likewise, the second component 874 comprises a buckle-beltmechanism that is connectable to the proximal end 816 of electrode strip815 and connectable to the proximal end 807 of the shield 804.

In some embodiments, the combination of the shield 804 and the electrodestrip 815 are delivered percutaneously in a minimally invasiveimplantation method, as schematically illustrated in FIGS. 30-32. Inparticular, because the electrode strip 815 is quite narrow (e.g., 3millimeters wide as shown in FIGS. 25-27), the procedure begins viamaking two small incisions 880, 882 in the skin 830 (and underlyingtissues/muscles 832) on opposite lateral sides of the underlying nerve840, as shown in FIG. 31. At least one of the incisions 880, 882 willhave a width (W6) generally corresponding to the width (W4 in FIG. 25)of the electrode strip 815. Using a forceps (not shown), the electrodestrip 815 is maneuvered through incision 880 and via incision 882 (asrepresented via arrows E and R) until the electrode strip 815 is inposition underneath nerve 840 with electrode contacts 820 in closecontact with the nerve 840 and facing skin 830, as shown in FIG. 30.Next, using a similar technique involving incisions 880 and/or 882, theshield 804 is introduced into a position interposed between nerve 840and skin 830. If necessary, either incision 880, 882 can be widenedslightly to accommodate introduction of the larger width (W5) of shield804 through the respective incision. With this minimally invasive methodof implantation, the sandwiched configuration of the electrode strip 815and the shield 804 relative to the nerve 840 is achieved with minimaldisruption to the skin and tissues above and near the nerve 840.Accordingly, the combination of the electrode strip 815 and the shield804 enable a minimally invasive method of implanting those elementswhile also providing a stimulation system that minimally impacts thenatural state of the nerve by acting as a cuff-less electrode.

Several different embodiments have been described in association withFIGS. 1-14, in which an IPG 55 is implanted in a pectoral region and inwhich a sensor electrode(s) and a stimulation electrode(s) (extendingfrom the IPG 55) are delivered percutaneously to sense respiratorypatterns and to apply a stimulation signal, respectively. In addition,several embodiments of stimulation electrode arrays (and associatedanchor mechanisms) have been described in association with FIGS. 15-32.Moreover, it is understood that in some of these embodiments, a lead ispercutaneously placed in each side of the body (left and right) suchthat bilateral (simultaneous or alternating) stimulation takes place onthe left and/or right hypoglossal nerve (or other target nerve). Withthese various embodiments in mind, it is further understood that amongthose embodiments, several configurations are provided in which at leasttwo electrodes are spaced apart in the body in the vicinity of the upperairway such that an impedance is measurable between the two spaced apartelectrodes to provide an indication of airway patency (e.g., openingand/or closing of the upper airway). In some configurations, the spacedelectrodes are both stimulation electrodes, while in otherconfigurations, the spaced apart electrodes comprise one stimulationelectrode and one respiratory sensor electrode. In yet otherconfigurations, the two spaced apart electrodes (used for measuring animpedance indicative of airway patency) include one of the electrodescomprising at least one of a stimulation electrode and a respiratorysensor electrode and the other one of the electrodes comprising anelectrode formed by an electrically conductive portion of a case orhousing of the IPG 55.

Moreover, in some embodiments, the respective electrode portions providea dual function in that each electrode provides a respiratory sensingfunction or a stimulation function as well as acting as a part of a pairof impedance sensing electrodes. On the other hand, in otherembodiments, at least one electrode of the pair of impedance sensingelectrodes does not also act to sense respiration (e.g. inspiration) orto stimulate but rather is dedicated for use in sensing impedance todetect or indicate a degree of airway patency.

At least some embodiments of the percutaneously-delivered electrodeportions (described herein) enable precise location of an electrodeportion adjacent to an optimal neurostimulation site because thepercutaneous approach enables the surgeon to vary the position of anelectrode portion of a stimulation lead along the length of thehypoglossal nerve. In addition, this precise placement is performed in aminimally invasive manner unlike the anatomically disruptiveconventional cut-down procedure for placing stimulation leads. Themethods and systems of the present disclosure allows the surgeon toidentify a precise optimal stimulation site that causes contraction ofone or more specific muscles (suited to restore airway patency) prior tofixing the location of the electrode portion relative to the targetnerve.

Embodiments of the present disclosure provide an implantable system toprovide therapeutic solutions for patients diagnosed with obstructivesleep apnea. The system is designed to stimulate the hypoglossal nerveduring inspiration thereby preventing occlusions in the upper airwayduring sleep.

While at least one exemplary embodiment has been presented in theforegoing detailed description, it should be appreciated that variationsexist. It should also be appreciated that the exemplary embodiment orexemplary embodiments are only examples, and are not intended to limitthe scope, applicability, or configuration of the present disclosure inany way. Rather, the foregoing detailed description will provide thoseskilled in the art with a convenient road map for implementing theexemplary embodiment or exemplary embodiments. It should be understoodthat various changes can be made in the function and arrangement ofelements without departing from the scope of the present disclosure asset forth in the appended claims and the legal equivalents thereof.

1. A method of implanting a stimulation lead to treat sleep-relateddisordered breathing, comprising: percutaneously inserting a distalportion of an introducing mechanism and positioning the distal portionto be adjacent to a target nerve stimulation site while maintaining aproximal portion of the introducing element external to a skin surface;and releasably engaging a stimulation lead relative to the proximalportion of the introducing mechanism, and slidably advancing thestimulation lead via the introducing mechanism to percutaneously insertthe stimulation lead until a distal portion of the stimulation lead ispositioned at the target stimulation site.
 2. The method of claim 1,removing the introducing mechanism while maintaining the position of thedistal portion of the stimulation lead at the target stimulation site.3. The method of claim 2, wherein maintaining the position of the distalportion of the stimulation lead includes: deploying an anchor mechanismto maintain the position of the distal portion at the target stimulationsite.
 4. The method of claim 3, wherein deploying the anchor mechanismincludes: locating the anchor mechanism at the distal portion of thestimulation lead.
 5. The method of claim 4, wherein the stimulation leadincludes a first side and a second side opposite the first side, andwherein locating the anchor mechanism includes: locating the anchormechanism on the second side of the distal portion of the stimulationlead.
 6. The method of claim 5, comprising: arranging the first side ofthe distal portion of the stimulation lead to include at least onestimulation electrode configured to releasably contact the nerve at thetarget stimulation site; and arranging the second side of the distalportion of the stimulation lead to include an insulating element tointerpose the insulating element between the nerve and the skin surface.7. The method of claim 5, wherein deploying the anchor mechanismcomprises: selectively releasing an array of members from a firststorage position against a body of the distal portion of the stimulationlead to a second deployment position to extend generally outward from abody of the distal portion of the stimulation lead.
 8. The method ofclaim 7, comprising: providing at least a portion of the introducingmechanism as a cannula and wherein slidably advancing the stimulationlead via the introducing mechanism includes slidably advancing thestimulation lead into and through the cannula; during advancement of thedistal portion of the stimulation lead through the cannula, maintainingthe respective member in the first storage position via engagement ofthe distal portion against an inner surface of the cannula; andreleasing the respective members of the stimulation lead from the firststorage position into the second deployment position upon removal of thecannula from the target stimulation site.
 9. The method of claim 8,wherein maintaining the respective flaps in the first storage positioncomprises: releasably covering the members with a distal extension ofthe cannula, wherein the distal extension defines an opening to exposethe electrode portion of the stimulation lead.
 10. The method of claim7, comprising: arranging the members as at least one of barbs or flaps11. The method of claim 1, comprising: removing the cannula whilemaintaining the distal portion of the stimulation lead at the targetstimulation site.
 12. The method of claim 1, wherein percutaneouslyinserting a distal portion of an introducing mechanism comprises:providing at least a portion of the introducing mechanism as a cannulaand wherein slidably advancing the stimulation lead via the introducingmechanism includes slidably advancing the stimulation lead into andthrough the cannula; arranging the cannula to include a flexible distalportion having a generally curved shape such that in a deploymentposition, an end of cannula is oriented in a direction oriented at agenerally obtuse angle relative to a longitudinal axis of a proximalportion of the cannula and in an insertion position, the flexible distalportion is configurable to assume an orientation generally parallel tothe longitudinal axis of the proximal portion of the cannula.
 13. Themethod of claim 12, comprising: upon positioning the distal portion ofthe stimulation lead at the target stimulation site, causing the distalflexible portion to assume the generally curved shape; slidablyadvancing the distal portion of the stimulation lead out of the end ofthe cannula until the distal portion is at the target stimulation site;removing the cannula while maintaining the distal portion of thestimulation lead at the target stimulation site.
 14. The method of claim13, comprising: locating an entry point of the cannula into the skinsurface at a first distance away from the target stimulation site,wherein the first distance is generally equal to a sum of: a seconddistance between the end of the cannula and a longitudinal axis of theproximal portion of the cannula when the distal portion is in thedeployment position; and a third distance corresponding to at most alength of an electrode portion of the stimulation lead.
 15. The methodof claim 13, comprising: via a percutaneous access, advancing a proximalportion of the stimulation lead from the target stimulation site to apectoral region of a patient.
 16. The method of claim 1, percutaneouslyinserting a distal portion of an introducing mechanism comprises:providing at least a portion of the introducing mechanism as a cannulaand arranging the cannula to include a generally rigid, straight distalportion having an opening oriented generally perpendicular to alongitudinal axis of the cannula; wherein slidably advancing thestimulation lead via the introducing mechanism includes slidablyadvancing the stimulation lead into and through the cannula to cause thedistal portion of the stimulation lead to extend out of the end of theopening until the distal portion of the stimulation lead is at thetarget stimulation site and in an orientation at a generally obtuseangle relative to the proximal portion of the cannula; and removing thecannula while maintaining the distal portion of the stimulation lead atthe target stimulation site.
 17. The method of claim 16, comprising:locating an entry point of the cannula into the skin surface at a firstdistance away from the target stimulation site, wherein the firstdistance is generally equal to a second distance corresponding to atmost a length of an electrode portion of the stimulation lead.
 18. Themethod of claim 1, comprising: upon advancing the cannula, measuring adepth of insertion of the distal portion via graduation markings spacedapart along a length of the cannula.
 19. The method of claim 1, whereinpercutaneously inserting a test needle comprises: percutaneouslyinserting the test needle at a plurality of test stimulation sites,including the target stimulation site; determining the targetstimulation site from among the plurality of test stimulation sites viaapplying, at each respective test stimulation site, a stimulationsignal; monitoring, during application of the stimulation signal, atleast one of: occurrence of a tongue protrusion or tongue retraction;change in a cross-sectional area of an upper airway; a lack of responsein non-target muscles; a twitch in a tongue muscle or laryngeal muscle;or strongest electromyography response for a target muscle.
 20. Themethod of claim 19, comprising: identifying, based on the determinedtarget stimulation site, a percutaneous access pathway to the targetstimulation site. 21-55. (canceled)